A Closer Look At The Mini-Open Ankle Arthrodesis

   Joint sparing procedures include total ankle arthroplasty, distraction arthrodiastasis and allograft total ankle replacement. However, the gold standard is still ankle arthrodesis.

   Traditional exposure for ankle arthrodesis has been through the open transfibular approach. This approach usually involves a fibular takedown osteotomy but researchers have described a medial malleolar approach.1 Unfortunately, this technique has the disadvantages of a larger skin incision that can lead to wound dehiscence and increased risk of postoperative infections, resection of the fibula and possible disruption of the vascular supply.

   In order to attempt to decrease the aforementioned disadvantages, arthroscopic ankle arthrodesis gained popularity. 2-5 This surgical technique has advantages of a high union rate with an early fusion time. It does have the disadvantages of a steep learning curve and the use of mechanical burrs to prepare the joint surfaces that can lead to thermal necrosis.

   Mini-open ankle arthrodesis combines the advantages of both open and arthroscopic ankle arthrodesis while minimizing the disadvantages. It preserves the fibula and the peroneal artery, and eliminates the need to use burrs to prepare the surfaces, which allows for earlier union. Since it has smaller incisions, it reduces the risk of wound dehiscence and postoperative infection.

What Are The Indications For The Procedure?

   An initial indication for mini-open ankle arthrodesis was ankle arthritis with minimal bone loss and minimal deformity that had failed conservative treatment. With experience, the indications have broadened for this technique.

   I have found that one can correct ankle deformities through the mini-open approach if the deformities meet certain criteria. I now use the mini-open approach in patients with varus or valgus deformity if the ankle range of motion is not rigid. I find that once you debride the remaining cartilage, you can correct any varus or valgus deformity. The surgeon can treat recurvatum and procurvatum deformities more appropriately through an open transfibular approach.

   The limited skin incisions make the mini-open ankle arthrodesis a better option for patients with dermatologic conditions, diabetes, autoimmune disorders, vascular conditions and previous incisions from prior surgeries. I still use a traditional open approach for rigid deformities, recurvatum or procurvatum of the ankle, talar avascular necrosis, nonunion revision or in ankles with significant bone loss.

A Guide To Surgical Technique

   The incisional approach for the mini-open ankle arthrodesis was originally described as anterior-medial and anterior-lateral incisions at the ankle approximately 1.5 to 2.0 cm in length. One would make the anterior-medial incision just medial to the tibialis anterior tendon and make the anterior-lateral incision just lateral to the peroneus tertius.

   With increased experience, I have found that one can lengthen the anterior-lateral incision slightly in the proximal direction in order to help facilitate screw placement. Carry dissection down to the anterior capsule and incise the capsule to expose the ankle joint.

   The surgeon should remove osteophytes and loose bodies in order to help with exposure of the joint. Debride both the medial and lateral gutters at this time. Visualize the joint by placing a smooth laminar spreader into one of the incisions. This allows good exposure to the joint through the second incision.

   Debride the cartilage using a combination of osteotomes and curettes. Straight curettes can debride the cartilage along the anterior tibia and talus. One can use curved osteotomes to facilitate the removal of cartilage from the middle and posterior tibial plafond. Take care not to penetrate the posterior ankle capsule. One can use curved ring curettes for the remaining cartilage on the talus.

   There is concern that removing cartilage along the posterior third of the talus can be difficult. I have found that the use of ring curettes allows safe and easy access to the posterior talus. After removing the cartilage, fenestrate the adjacent surfaces using a fish scale technique with an osteotome and mallet. Then position the talus within the ankle mortise and place temporary fixation wires. Check the position visually and via fluoroscopy.

   Once you have achieved satisfactory alignment, place the screws. Three screws are preferable to stabilize the joint for arthrodesis. The surgeon has the option of using cannulated or solid screw fixation. The first screw is considered the “home run screw.” Place this screw from the posterior aspect of the tibia into the head and neck of the talus. Make the incision between the lateral Achilles tendon and the sural nerve. A good aiming position is the course of the first metatarsal. Use fluoroscopy to confirm the location of this screw. This screw is typically 60 to 70 mm in length.

   Place the second screw from the lateral-distal tibia into the posterior-lateral aspect of the talus. The starting position of this screw is the reason for extending the anterior-lateral incision slightly more proximal. The third screw’s starting position is just proximal to the medial malleolus and extends inferior-lateral to the distal-lateral aspect of the talus. Both of these screws are approximately 40 to 45 mm in length.

   A washer is recommended for the third screw in order to increase the surface area. When inserting the second and third screws, alternating tightening between the two screws will prevent any rotation of the talus. Fluoroscopy confirms the placement of the screws. Take care to avoid placement of the second or third screws into the subtalar joint.

   Then pack the bone graft into the medial and lateral gutters and along any voids within the ankle. Close the incision by layers.

What You Should Know About Postoperative Care

   Patients wear a non-weightbearing compression splint for two weeks. Follow this with the use of a non-weightbearing cast for an additional two weeks.

   Obtain X-rays at the four-week post-op visit. If the patient’s pain is under control without tenderness to palpation or excessive swelling, and the radiographs are stable, place the patient in a weightbearing cast and allow him or her to bear weight as tolerated. Obtain X-rays every four weeks and keep the patient in a weightbearing cast until he or she achieves radiographic consolidation.

   Most patients are out of the cast and into a cast boot at two and a half to three months after the surgery. If there is any doubt of joint stability, keep the patient in a cast. Once the patient is weightbearing in shoes, a rocker bottom shoe is recommended to help compensate due to the lack of ankle joint motion.

Final Notes

   While the current literature is lacking with this technique, the limited studies have shown very favorable results. Paremain, et al., and Miller, et al., showed a 100 percent and 96.8 percent union rate at a mean time of six weeks and eight weeks respectively. 4-7

Dr. Grambart is the foot and ankle surgeon for Carle Clinic Association, Division of Orthopedics in Champaign, Ill. He is a clinical instructor at the University of Illinois School of Medicine. Dr. Grambart is a Fellow of the American College of Foot and Ankle Surgeons.
Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons, and is board-certified in foot and ankle surgery. He is in private practice in Little Rock, Ark.

References:

1. Schuberth JM, et al. The medial malleolar approach for arthrodesis of the ankle: a report of 13 cases. J Foot Ankle Surg, 2005. 44(2):125-32. 2. Collman DR, Kaas MH and Schuberth JM. Arthroscopic ankle arthrodesis: factors influencing union in 39 consecutive patients. Foot Ankle Int, 2006. 27(12):1079-85. 3. Ferkel RD and Hewitt M. Long-term results of arthroscopic ankle arthrodesis. Foot Ankle Int, 2005. 26(4):275-80. 4. Myerson MS and Quill G. Ankle arthrodesis. A comparison of an arthroscopic and an open method of treatment. Clin Orthop Relat Res, 1991(268):84-95. 5. Raikin SM. Arthrodesis of the ankle: arthroscopic, mini-open, and open techniques. Foot Ankle Clin, 2003. 8(2):347-59. 6. Miller SD, Paremain GP and Myerson MS. The miniarthrotomy technique of ankle arthrodesis: a cadaver study of operative vascular compromise and early clinical results. Orthopedics, 1996. 19(5):425-30. 7. Paremain GD, Miller SD and Myerson MS. Ankle arthrodesis: results after the miniarthrotomy technique. Foot Ankle Int, 1996. 17(5):247-52.